Aviation Accident Report: Pennsylvania Central Airlines Flight 19/Appendix B

APPENDIX 3

Weather Analysis

The weather analysis for August 31, 1940, prepared by meteorologists is as follows: A weak occluded low pressure area was located over the Lake Superior region, with its principal front occluded at the center of the system, becoming a cold front of weak intensity extending from the central portion of Lake Erie south-southwestward across Ohio, where it became too diffuse to remain of any importance. There were indications of a cold front of more active nature running from the center of the depression south and southwestward across Lake Michigan to the Missouri-Iowa state line, where it also became too diffuse to be carried any further. East of Illinois the pressure gradient was comparatively flat. An anti-cyclonic circulation prevailed along the Coast north of the Virginia Capes produced by a high pressure system situated some distance off shore in the Cape Cod area. The very sluggish circulation resulting from this pressure distribution and the saturated state of the lower layer was such that a widespread low cloud deck, with considerable fog, was reported in all sections of the area extending from the northern Smoky Mountains northeastward to the central St. Lawrence Valley.

The meteorologists stated that while the fronts did not exert a dominating influence over weather conditions in any section southeast of the Lakes, the approach of any front, no matter how weak, would contribute to the vertical lifting of an air mass which was already being acted upon by other forces such as convergence, aerographic lift, etc. There was no temperature differential in the horizontal between Pittsburgh and Washington.

The tropical hurricane which was reported moving slowly northeastward over the South Atlantic was considered by the weather experts as being too far removed at any time during the period under consideration to be an influencing factor. The above analysis was based entirely upon a synoptic weather map with upper air directions and velocities and available radiosonde data superimposed.

 

Weather Forecast

The following is the airway forecast issued by the Cleveland station of the U.S. Weather Bureau for the period 11:30 A.M. to 7:30 P.M. (EST), for the route Detroit to Washington:

"Weak low pressure central over eastern Lake Superior and northern Lake Michigan with poorly defined and weak cold front near Indianapolis, Grand Rapids, and north westward at 7:30 A.M. Pressure gradient is very flat throughout this district. Cloudiness will increase to broken or overcast to westward of mountains with ceiling 4 to 7000 and lower clouds 2 to 4000 variable scattered to broken first quarter and broken to overcast thereafter. Scattered showers in afternoon and some mild thunderstorms probable central Michigan, eastern Indiana and western Ohio second half period. Overcast to occasionally broken clouds mountains eastward with fog diminishing and ceiling lifting to 6 or 800 over higher terrain and 1 to 2000 ground scattered showers through mountains and some mild thunderstorms likely in afternoon. Local areas of very low to low visibility with fog slowly dissipating over middle and eastern ridges first quarter but improving to between 1 and 3 in afternoon hours and to between 6 and 3 other sections. Visibility between 5 and 10 westward of mountains. Winds aloft 250 to 270 degrees 20 to 30 mph."

The trip forecast issued to the captain by the company's meteorologist was as follows:

"Trip 19 forecast:

"Washington to Pittsburgh - cruising altitude 6000 feet, wind 260°, 10 mph, temp. 66.

"Pittsburgh to Cleveland - cruising altitude 2500 feet, wind 280°, 10 mph, temp. 76.

"Cleveland to Detroit - cruising altitude 4000 feet, wind 220°, 30 mph, temp. 72.

"Overcast to broken, Washington to Pittsburgh, base 1500, Washington area top 5500 over ridges stop broken to scattered, Pittsburgh to Detroit, base 5000 lowering to 3000 in scattered mild to moderate thunderstorms stop.

"All terminals scattered to broken at 5000 lowering to 2000 in thunderstorms, visibility unlimited, lowering to 3 in storms signed Coons Pittsburgh 12:30 p.m."

The sequence weather reports and forecasts available to Captain Scroggins at the time of scheduled departure, 1:50 P.M. (EST) and which appeared on the clearance, were as follows:

12:35 p.m., EST - Washington, D.C. C (satisfactory for flight under contact flight rules) Ceiling estimated 1400 feet overcast lower broke clouds, visibility 7 miles, light rain shower, pressure 1017.3 millibars, temp. 78, dewpoint 74, wind SW 5, altimeter setting 30.03.

Frederick, Maryland. Special observations^[1] Ceiling estimated 900 feet, overcast lower broken clouds, visibility 6 miles, light rain, temp. 78, dewpoint 74, wind WSW 7.

Front Royal, Va. Ceiling estimated 3500 feet, high broken lower broken clouds, visibility unlimited, pressure 1016.9 millibars, temp. 80, dewpoint 73, wind N 3, altimeter setting 30.03, scattered clouds at 2000 feet, thunderheads all quadrants.

Martinsburg, W. Va. Special observation. Ceiling estimated 3800 feet, overcast lower broken clouds, visibility 7 miles, pressure 1017.3, temp. 74. dewpoint 71, wind NW 8. altimeter setting 30.04.

Elkins, W. Va. Ceiling estimated 4000 feet, overcast lower scattered clouds at 800 feet, visibility 5 miles, light ground fog, pressure 1018.3 millibars, temp?9, dewpoint 66, wind SE 4, altimeter setting 30.11, west ridge obscured.

Middletown, Pa. Special observation. Ceiling estimated 1200 feet, overcast, visibility 5 miles, light fog, pressure 1016.9 millibars, temp. 75, dewpoint 71, wind WNW 10, altimeter setting 30.02 lower scattered clouds at 800 feet.

Harrisburg, Pa. C (satisfactory for flight according to contact flight rules) Ceiling estimated 1000 feet, overcast lower scattered clouds at 800 feet, visibility 4 miles, moderate rain showers pressure 1016.6 millibars, temp. 72, dewpoint 72, wind NW 3, altimeter setting 30.02.

Cove Valley, Pa. Special observation. Ceiling 3000 feet, overcast lower broken clouds, visibility 7 miles, pressure 1017.6 millibars, temp. 72, dewpoint 68, wind missing, altimeter setting 30.07, overcast at 6500 feet.

Buckstown, Pa. Special observations. Ceiling estimated 7000 feet, overcast lower scattered clouds at 2000 feet, visibility 7 miles, pressure 1017.3 millibars, temp. 70, dewpoint 64, wind S 3, altimeter setting 30.12, break in overcast.

Pittsburgh, Pa. C (satisfactory for flight according to contact flight rules) Special observation. Ceiling estimated 2500 feet, overcast thin lower broken clouds, visibility 4 miles, light rain shower, light smoke, pressure 1017.6 millibars, temp. 69, dewpoint 65, wind WNW 2, altimeter setting 30.07.

East Liverpool, Ohio. Ceiling estimated 3500 feet, high and lower broken clouds, visibility 4 miles, hazy, pressure 1017.3 millibars, temp. 74, dewpoint 68, wind S 4, altimeter setting 30.05.

Cambridge, Ohio. Ceiling estimated 2500 feet, broken lower broken clouds visibility 8 miles, pressure 1017.3 millibars, temp. 81, dewpoint 66, wind W 7, altimeter setting 30.05.

Akron, Ohio. C (Satisfactory for flight according to contact flight rules) Ceiling unlimited high broken clouds lower scattered clouds at 35000 feet visibility unlimited, pressure 1018.0 millibars, temp. 79, dewpoint 50, wind SE 4, altimeter setting 30.08.

Cleveland, Ohio. C (satisfactory for flight according to contact flight rules) Ceiling unlimited scattered clouds at 8000 feet, visibility unlimited, pressure 1017.6 millibars, temperature 79, dewpoint 52, wind SSW 2, altimeter setting 30.05.

The 1:35 p.m. weather sequence may have been available to Captain Scroggins prior to departure from Washington, since the departure of the trip was delayed, or he may have obtained the weather data from this sequence by listening in on the Washington radio range frequency.

Washington, D.C. C ( satisfactory for flight according to contact flight rule) ceiling estimated 1500 feet, overcast lower broken clouds, visibility 5 miles, light rain shower, pressure 1016.3 millibars, temp. 76. dewpoint 72, wind SW 10, altimeter setting 30.00.

Frederick, Md. Ceiling estimated 1000 feet, overcast lower broken clouds, visibility 1-1/2 miles, light thunderstorms, moderate rain, light fog, temp. 77, dewpoint 75, wind SW 12.

Front Royal, Va. Ceiling estimated 2500 feet, broken clouds lower broken clouds, visibility unlimited, light rain showers, pressure 1015.6 millibars, temp. 76, dewpoint 74, wind calm, altimeter setting 29.99

Martinburg, W. Va. Ceiling estimated 6000 feet, broken clouds lower scattered clouds at 4000 feet, visibility 7 miles, pressure 1016.3 millibars, temp. 78, dewpoint 70, wind NNW 4, altimeter setting 30.01.

Elkins, W. Va. Ceiling estimated 6000 feet, overcast lower scattered clouds at 800 feet, visibility 7 miles, pressure 1017.6 millibars, temp. 72, dewpoint 63, wind SE 4, altimeter setting 30.10.

Middletown, Pa. Special observation. Ceiling estimated 1200 feet, overcast lower broken clouds, visibility 2 miles, light rain shower, light fog, pressure 1016.9 millibars, temp. 72, dewpoint 70, wind WNW 12, altimeter setting 30.02, conditions extremely variable.

Harrisburg, Pa. N (satisfactory for flight under instrument flight rules) Special observation taken at 1:37 p.m. EST. Ceiling estimated 800 feet, variable overcast, visibility 1-1/4 miles, variable light thunderstorm, heavy rain shower, pressure 1016.3 millibars, temp. 72, dewpoint 71, wind SE 5, altimeter setting 30.01

Cove Valley, Pa. Ceiling estimated 3000 feet, overcast lower broken clouds, visibility 8 miles, pressure 1017.3 millibars, temp. 74, dewpoint 68, wind clam, altimeter setting 30.06, overcast at 6500 feet.

Buckstown, Pa. Ceiling estimated 7000 feet, high overcast lower broken clouds, visibility 8 miles, pressure 1015.9 millibars, temp. 74, dewpoint 64, wind SW 3, altimeter settings 30.39, lower, overcast to the east.

Pittsburgh, Pa. C (satisfactory for flight according to contact flight rules) Ceiling estimated 2500 feet, overcast thind lower broken visibility 4 miles, light thunderstorm light rain shower, light smoke, pressure 1016.9, temp, 68, dewpoint 66, wind NW 9, altimeter setting 30.06, overcast at 5000 feet.

East Liverpool, Ohio. Special observation. Ceiling estimated 4000 feet, high and lower broken clouds, visibility 4 miles, hazy, pressure 1016.9 millibars, temp. 77, dewpoint 68, wind NW 4, altimeter setting 30.04, wind shifted from the south at 1:35 p.m.

Cambridge, Ohio. Ceiling estimated 3000 feet, broken clouds, visibility 9 miles, pressure 1016.6 millibars, temp. 80, dewpoint 63, wind WNW 10, altimeter setting 30.03.

Akron, Ohio. C (satisfactory for flight according to contact flight rules) Ceiling unlimited, high scattered clouds lower scattered clouds at 4000 feet, visibility, unlimited, pressure 1016.3 millibars, temp. 81, dewpoint 49, wind S 4, altimeter setting 30.02.

Cleveland, Ohio. C (satisfactory for flight according to contact flight rules) Ceiling unlimited, clear visibility, unlimited, pressure 1016.3 millibars, temp. 83, dewpoint 56, wind SSW 7 altimeter setting 30.01.

1. A "special observation" is one taken between regular reporting times. Its purpose if to report abrupt and extensive changes in the weather.